Question

Without referring to Figure 9.1 , write Lewis dot symbols for atoms of the following elements: (a) Be, (b) \(\mathrm{K},\) (c) \(\mathrm{Ca},\) (d) \(\mathrm{Ga},\) (e) \(\mathrm{O},\) (f) \(\mathrm{Br},(\mathrm{g}) \mathrm{N},(\mathrm{h}) \mathrm{I},\) (i) \(\mathrm{As}\), (j) F.

Short answer

The Lewis dot symbols for the given elements are: (a) Be : \( \mathrm{Be:.} \), (b) K : \( \mathrm{K:.} \), (c) Ca : \( \mathrm{Ca:.} \), (d) Ga : \( \mathrm{Ga:..:..:..:..} \), (e) O : \( \mathrm{O:..:..:..:..:..:..} \), (f) Br : \( \mathrm{Br:..:..:..:..:..:..:..:..} \), (g) N : \( \mathrm{N:..:..:..:..:..} \), (h) I : \( \mathrm{I:..:..:..:..:..:..:..:..} \), (i) As : \( \mathrm{As:..:..:..:..:..} \), (j) F : \( \mathrm{F:..:..:..:..:..:..:..} \).

Step-by-step solution

Determine the number of valence electrons

List the given elements and identify which group (column) they fall into on the periodic table. The group number of an element (excluding transition metals) corresponds to the number of valence electrons.

Write Lewis dot symbols

Now that you know the number of valence electrons, you can write the Lewis dot symbols. Represent each valence electron as a dot around the chemical symbol. Dots are first drawn on the four sides (above, below, left and right) each representing one pair. After each side has one dot, pairs can be made by adding a second dot. The dots were placed in a counter-clockwise formation, but it isn't necessary.

Repeat process for each element

Repeat step 1 and step 2 for all the given elements in the exercise.

Key concepts

Valence Electrons

Valence electrons are the electrons that reside in the outermost shell of an atom and are essential for forming chemical bonds with other atoms. Understanding valence electrons is crucial as they determine how an element will react chemically.

For instance, an atom like oxygen (O), which is in group 6 of the periodic table, has six valence electrons. These electrons are represented as dots in the Lewis dot symbol, which provides a visual way to consider possible bonding scenarios for atoms.

To grasp the concept of valence electrons effectively, let's look at a simple method. Identify the element's group number on the periodic table. For groups 1 and 2, and 13 to 18, the group number corresponds to the number of valence electrons (with the exception of the transition metals). So, an element in group 1 would have one valence electron, while an element in group 15 would have five. By having a clear understanding of valence electrons, you pave the way for exploring the nature of bonds that atoms can form, which is fundamental in learning chemistry.

Periodic Table Groups

The periodic table is organized into rows and columns known as periods and groups respectively. Groups are particularly helpful when predicting the properties of an element, including valence electrons. Each group contains elements with the same number of valence electrons, thus exhibiting similar chemical behavior.

For elements in groups 1 and 2 (the alkali and alkaline earth metals) and groups 13 to 18, we can easily determine the number of valence electrons. For example, all elements in group 1 have one valence electron, group 2 have two, and so on, up to group 18, which have eight (except for helium, which has two).

Looking at the exercise, to determine the valence electrons of element K (potassium), found in group 1, we can directly say it has a single valence electron, crucial for its reactivity and bonding potential. Understanding periodic table groups is key to predicting how elements will interact with each other, making the process of learning chemistry more structured and manageable.

Chemical Symbols

Chemical symbols are shorthand representations of chemical elements, derived from either English or Latin names. These one- or two-letter symbols provide a global standard for communicating chemical information. For example, 'H' represents hydrogen, and 'O' for oxygen.

When dealing with Lewis dot symbols, chemical symbols are the starting point around which we illustrate valence electrons as dots. It is important to write the correct chemical symbol before adding any dots to prevent confusion, particularly when elements have symbols that are similar. For example, Gallium (Ga) and Gallium Arsenide (GaAs) have distinct properties and uses, and mistaking one symbol for the other in chemical equations or Lewis structures can lead to significant errors.

By always double-checking the chemical symbol against the periodic table, students can avoid mistakes and ensure clear communication of chemical concepts. This practice is especially important in complex reactions and when learning about the formation and characteristics of various chemical bonds.